I would drop the Stat increase and change take damage to when attacked, after the attack is resolved. So you could disengaged when missed. I would also require you to be wearing light armor to use that reaction.

Considering this one feats gives the same exact bonus as the swift feat, AND a +1 to an ability, AND the ability to disengage as a reaction I would say this is way overpowered.

And by the way, disengage doesn’t actually allow you to move. It just makes your movement for that turn not provoke attacks of opportunity. So unless you have a way to move on someone else’s turn that doesn’t also use your reaction, the last part is probably not what you meant to say. I’m guessing you meant “disengage AND move” which would make the feat even more ridiculously overpowered. That would be giving you an action and a move action (aka a whole turn besides the bonus action) as a reaction. At will.

I would say this is at least two and half feats all wrapped up in one. That all being said, I love the idea of a Light Armor Mastery feat.